Not true actually. Coloured signs are vanilla, they just cannot be placed without an external editor (like MCEdit). You do not have to mod your game for this to happen. Oh, and confirmed on a MacBook Air running Mountain Lion and Minecraft 1.5.1
Comfirmed using unjailbroken iPod 4G on 0.6.1
It wasn't working if I turned my sound up and had my music off. I am not confusing this with MC-22, though I did notice that happening.
Not true actually. Coloured signs are vanilla, they just cannot be placed without an external editor (like MCEdit). You do not have to mod your game for this to happen. Oh, and confirmed on a MacBook Air running Mountain Lion and Minecraft 1.5.1